1. Field of the Invention
The present invention relates generally to a pneumatic tool, and more particularly to a monodirectional intake pressure stabilization structure of pneumatic tool.
2. Description of the Related Art
A pneumatic tool is powered by a compressed air source. Through internal forward or backward air passage of the pneumatic tool, external high-pressure air is guided into internal air chamber of the pneumatic tool for driving a rotor. The rotor further drives an output shaft to forward rotate or backward rotate to output power for operation. In general, the flow of compressed air entering the pneumatic tool can be changed to adjust the forward rotational speed and output torque. On the other hand, with respect to the backward rotation, the compressed air often enters the air chamber at a maximum flow for outputting maximum torque in accordance with the torque requirement of actual operation, for example, screwing and unscrewing of a forward worm.
However, the pressure value of the compressed air provided for the pneumatic tool is unstable. In general, the pressure value of the compressed air provided by an air compressor ranges from about 70 psi to 270 psi. Therefore, in the case that the compressed air is supplied to the pneumatic tool in an uncontrolled or unstable state, the output torque is hard to be stable. As a result, even after the flow of compressed air for forward rotation is regulated, the pneumatic tool may still output excessively great and unstable torque. This may lead to damage of the work piece.
U.S. Pat. No. 4,834,131 discloses a pneumatic tool in which a safety valve is arranged between the pneumatic tool and the compressed air source. In the case that the pressure value of the compressed air exceeds a set value, the compressed air will be released to the atmosphere before entering the pneumatic tool so as to obviate the defect existing in the prior art. Such technique is able to avoid over torque in forward rotation. However, such measure will also reduce the maximum torque value in backward rotation. Accordingly, it is impossible to take both situations into consideration. Taiwanese Patent No. 095131045 discloses an improved technique in which the safety valve is inbuilt in the cylinder of the pneumatic tool as a part thereof. Such safety valve is able to release the over high-pressure air to the exterior of the pneumatic tool. Such technique helps in stabilizing the pressure. However, such technique is still unsatisfactory.